Pneumatic outlets have heretofore been provided having a tubular conduit projecting from a side of the outlet to which a single size of hose coupling may be attached to apply suction of air under pressure to unload the outlet. A pneumatic outlet of this type is shown and disclosed in U.S. Pat. No. 3,778,114. If a different size of hose is to be used, a special adapter must be provided. The adapter, however, must be removed when changing coupling sizes, and such adapters may be easily misplaced or lost.
It has also been proposed in U.S. Pat. No. 3,048,448 to provide a pair of nested concentric tubes to which male hose couplings of different diameters may be applied with a coupling of smaller diameter being received within the inner tube and a coupling of larger diameter being received within the outer tube. Such an arrangement, however, is not adapted to receive female hose couplings of different diameters, and special adapters would have to be used to accommodate female hose couplings of different diameters.